This invention relates to combinations of tools and methods used to prepare a socket in a femur for receiving a femoral prosthesis.
One common type of femoral prosthesis includes a stem portion adapted to be inserted and fixated (as by cement) in a socket rasped into the proximal femur of a patient, a ball portion adapted to project and engage a cup implanted in the pelvis of the patient, and a collar between the stem and ball portions adapted to rest against the calcar forming the medial wall portion of the femur at the inlet to the socket to help bear the load applied to the femur through the prosthesis. Some experts feel that the fit between the collar and the calcar must be very precise, or such loads will be borne only by the stem portion; and that this lack of loading on the calcar of the inlet to the socket will cause it to resorb or be dissolved by the body, thereby weakening the side walls forming the socket that support the stem portion so that the stem portion may eventually loosen in the femur.
For this reason, a calcar rasp set is presently available that includes a guide member including a stem portion shaped like the stem portion of a femoral prosthesis and a pilot post portion projecting from its stem portion; and a rotary rasp adapted to be journaled on the pilot post portion and manually rotated. After a socket is formed in a femur through the use of a conventional rasp having a handle permanently attached at one end, and before the stem portion of the femoral prosthesis is positioned and fixated in the socket, the stem portion of the guide member is inserted into the socket so that the pilot post portion projects from the femur, and the rotary rasp is journaled on the pilot post portion and manually rotated so that the rasp faces the surface of the calcar around the inlet to the socket.
These tools and method of facing the calcar around the socket may not be as precise as may be desired, however, since any differences in size between the stem portion of the guide member and the socket could cause the stem portion of the guide member to be off center in the socket and the resultant facing of the calcar to be inaccurate with respect to the collar of a femoral prosthesis subsequently fixated in the socket.